1. Field of the Invention
The present invention relates generally to control devices for controlling operation of fluid-supplying machines or apparatus used in medical procedures such as angiography and, further, to hand-held control devices for controlling the flow rate of fluids, such as contrast media or common flushing agents, injected into a patient during medical procedures, such as angiography.
2. Description of Related Art
Angiography is a procedure used in the detection and treatment of abnormalities or restrictions in blood vessels. During angiography, a radiographic image of a vascular structure (i.e., blood vessel) is obtained by injecting radiographic contrast material, also referred to as contrast media, through a catheter into a vein or artery. X-rays are passed through the region of the body in which the contrast media is concentrated. The X-rays are absorbed by the contrast material, causing a radiographic outline or image of the blood vessel containing the contrast media. The X-ray's images of the blood vessel filled with the contrast media are usually recorded onto film or videotape and are displayed on a fluoroscope monitor.
Many angiographic procedures, in particular coronary angiography and especially coronary vascular interventional procedures such as angioplasty, require frequent intermittent injections of contrast media. The contrast media is administered in varying volumes as well as modulated strengths and time durations. The intermittent contrast media injections are critical for optimal positioning of guiding catheters at the targeted blood vessels, positioning of guide wires to and through the targeted areas during catheter interventions (e.g. percutaneous transluminal coronary angioplasty), and for assessment of the results of such interventional procedures.
During angiography, after a physician places the angiographic catheter into a vein or artery, the angiographic catheter is connected to either a manual or an automatic contrast media injection mechanism. A typical manual contrast media injection mechanism includes a syringe and a catheter connection. The user of the manual contrast media injection mechanism adjusts the rate and volume of injection by altering the manual actuation force applied to the plunger of the syringe.
Automatic contrast media injection mechanisms typically involve a syringe connected to a linear actuator. The linear actuator is connected to a motor, which is controlled electronically. The operator enters into the electronic control a fixed volume of contrast media and a fixed rate of injection. There is typically no interactive control between the operator and the mechanism, except to start or stop the injection. A change in flow rate occurs by stopping the mechanism and resetting the parameters.
Recent improvements in the radiographic imaging field have attempted to apply software and hardware interfaces to automatic contrast media injection mechanisms to provide variable flow rate and fixed flow rate modes to the operator. Additionally, the delivery of common flushing agents, such as saline, may also be controlled using the software/hardware interfaces. One such angiographic control device is disclosed in U.S. Pat. No. 5,515,851 to Goldstein. The Goldstein patent discloses the use of a microchip control device in the form of an angiographic control pad device designed to facilitate finger touch modulation of flow rate, volume, and duration of contrast media injection into a patient during an angiographic procedure. The control finger pad device allows the operator to control the aforementioned parameters during an injection procedure by altering the duration and extent of fingertip depression on the finger pads.
Another control device used to provide variable flow rate control to an operator of an automatic contrast media injection mechanism is disclosed in U.S. Pat. No. 5,916,165 to Duchon et al. This reference discloses a hand-held pneumatic control device that interfaces with and controls a fluid supply or injection mechanism. The hand-held control device is further adapted to control dispensement of saline injected into the patient during the angiographic procedure. The hand-held control device is generally adapted to be responsive to fluid pressure within the device. The control device includes a pressure control member adapted to selectively change fluid pressure within the pressure control member based on inputs from the operator. In one embodiment, the control device is provided with one or more internal air bladders having a volume that selectively adjusts to change the fluid pressure within the air bladders based on operator inputs. Internal sensors are provided to monitor the volume changes of the air bladders, and generate control signals based on the volume changes.
U.S. Pat. No. 5,988,587, also to Duchon et al., discloses another version of a hand-held control device for an automatic contrast media injection mechanism. This reference discloses a hand-held control device that includes two opposing and spaced-apart handles. A resilient attachment member connects the two handles. The resilient attachment member is configured to allow the first handle to move with respect to the second handle in response to operator inputs. The control device includes a sensor attached to the first handle for producing a variable control signal indicative of the distance between the first handle and the second handle.
Yet another hand-held control device is disclosed in U.S. Pat. No. 6,221,045 to Duchon et al. This reference discloses a hand-held control device that generates a control signal that is continuously variable according to continuously varying movement of a user's hand on the hand-held control. The control signal is continuously variable and sustainable at any value between preset maximum and minimum values corresponding to maximum and minimum contrast media discharge flow rates.
As automatic contrast media/fluid injection mechanisms and systems become more complex, it is desirable to interface with such mechanisms and systems on a digital level to afford more control over the medical injection procedures performed with such devices. The foregoing examples of hand-held control devices provide a certain amount of control over such procedures by offering the operator of the contrast media/fluid injection mechanism or system a variable flow rate mode of operating the mechanism or system. However, there is room for improvement in the field of control devices for controlling or operating contrast media/fluid injection mechanisms or systems, for example by providing a control device that may interface with such mechanisms or systems on a truly digital level, while providing accurate flow rate control of contrast media injection and saline flush control. Additionally, there is a need for a hand-held control device that is simple to use, for example, having an intuitive look and feel of operation for the operator. Further, a need exists for a hand-held control device that is simple and inexpensive to manufacture, so that the device itself may be disposable after a preset number of uses.